There are a large number of published reports implicating activation of the coagulation mechanism as part of the pathophysiology of cancer growth and metastasis. We are using a radioimmunoassay to measure plasma fibrinopeptide A (FPA), an immediate and specific product of the fibrinogen to fibrin conversion, as an indicator of rates of ongoing coagulation in patients with cancer. In the preliminary phase of this project we have been able to show that mean levels of this peptide are significantly elevated in cancer patients compared to normal, and that the FPA levels rise in patients with rapidly growing tumors. We will continue these studies, and in collaboration with Dr. Richard Edwards will study the association between endogenous peripheral blood mononuclear cell tissue factor activity and FPA levels. A statistically significant correlation between these two parameters will suggest that immune recognition of tumor cells by T lymphocytes activates monocytes to become phagocytic, and concomitantly produce higher than normal levels of tissue factor activity on their surfaces. This could explain the increase in FPA levels in patients with growing tumors.